EXPERIMENTAL INVESTIGATION OF DRAG REDUCTION ON AHMED CAR MODEL USING A COMBINATION OF ACTIVE FLOW CONTROL METHODS

Abstract

Aerodynamic drag is an important factor in vehicle's fuel consumption. Pressure drag which is the main component of total drag is a result of boundary layer separation from vehicle surface. In this paper, we investigate experimentally, the effect of suction and base bleeding as two active flow control methods on aerodynamic drag reduction of Ahmed body with 35 degree rear slant angle. Suction in boundary layer is applied in order to delay flow separation by extracting flow particles with low kinetic energy near the model surface and the sucked air is blown into the wake of the model to increase the static pressure of the wake region. The location of suction is at the beginning of rear slant surface and the location of blowing is at the middle part of rear vertical part of the model. Moreover, the effect of change in control flow rate and suction and base bleeding area is investigated. Strong suction leads to drag reduction and when suction is accompanied by base bleeding more drag reduction can be achieved. Furthermore, for a constant control flow rate, smaller suction area and bigger base bleeding area yield to more reduction in drag.